Foam Prevention In The Reverse Flotation Process For Purifying Calcium Carbonate

ABSTRACT

This invention relates to an composition, comprising
     A) at least one quaternary ammonium compound which is a collector for the reverse flotation of magnesium minerals from calcium carbonate   B) at least one antifoam agent   C) a solvent
 
and its use in the reverse flotation of calcium carbonate.

Object of this invention is an improved process for purifying calciumcarbonate from silicate-magnesium mineral as impurity. The use ofquaternary ammonium compound as collector in this process is well known.However, besides their collector function, quaternary ammonium compoundsproduce stable foam, what is undesirable for the next mineral processingstep. This invention provides a new low foam composition comprising anantifoam compound and a quaternary ammonium compound used in a reverseflotation process for purifying calcium carbonate fromsilicate-magnesium impurities. The composition of the present inventionis able to float said impurity mineral without producing undesirablefoam.

The present invention describes a process for purifying calciumcarbonate ore containing magnesium silicate mineral as impurity. Suchmagnesium silicates are for example the minerals of the biotite group,such as flogopite and micas. The inventive process uses a reverse frothflotation, in which the magnesium silicate gangue mineral is floated anda concentrate containing calcium carbonate remains in the bottom of theflotation cell.

The purified calcium carbonate, depleted from silicate-magnesiummineral, is used as raw material, particularly in the cement industry.The cement industry needs a calcium carbonate with a low MgO grade inorder to avoid the reaction between MgO and water (hydration). TheMg(OH)₂ (hydrate compound) has a higher volume than MgO and its volumeincrease weakens the cement after hardening. The calcium carbonatepurified by the inventive process is a calcium carbonate with a low MgOcontent and a high CaO-mass recovery.

In the froth flotation process, minerals are separated using air bubblesin water as vehicle. For the solid mineral particles to float, theirsurface must be made hydrophobic by using a collector. The mineralsurface made hydrophobic adheres at the air bubbles and causes theparticles to float. Thereby, a mineralized froth is formed at the top ofthe flotation cell. It is desired that the mineralized froth has arestricted degree of stability. It should be stable enough to overflowthe cell without losing the attached solid particles, but it shouldbreak down after entering into the tailing dam.

The separation of calcium carbonate from impurities by reverse frothflotation is known in the art. Particularly, the use of quaternaryammonium compounds as collector in the calcium carbonate ore flotationis well known. Quaternary ammonium compounds used typically comprise avariety of chain lengths and saturation degrees of the hydrocarbongroups. Quaternary ammonium compounds are used in the present inventionas collector to achieve the low magnesium oxide grade besides a highcalcium oxide grade and high recovery.

U.S. Pat. No. 4,995,965 discloses a process for purifying calciumcarbonate ore containing silicate impurities using a collector ofmethyl-bis(2-hydroxypropyl) cocoammonium methyl sulfate.

U.S. Pat. No. 5,261,539 discloses a reverse flotation process forpurifying calcite ore, calcite rougher or calcite concentrated wherebyfinely ground particles thereof are contacted with a flotation agent andfloated to remove quartz, micaceous minerals, chlorite, pyrite and othermineral impurities, the improvement which comprises using a flotationagent consisting essentially of a compound selected from the groupconsisting of an alkoxylated C₈-C₂₄-alkyl guanidine containing 1-10alkoxy groups, an alkoxylated C₈-C₂₄-alkyl fatty amine containing 1-6alkoxy group and mixtures thereof.

U.S. Pat. No. 5,720,873 discloses a method of cleaning calcium carbonateore containing silicate impurities in the presence of a quaternaryammonium compound and an alkylene oxide adduct of an amine compound andthe weight ratio between the related products are 3:2-11:1.

EP-2012930 B1 discloses reverse froth flotation processes for treating acalcium carbonate are containing silicates using fatty-di-lower-alkylbenzyl quaternary ammonium compound, and di-fatty di-lower-alkylquaternary ammonium compound.

The cited art does not address the problem of persisting froth.

The mineral-collector interactions strongly affect the degree of frothstabilization achieved. Apart from making the mineral particleshydrophobic, the collector also increases the bubbles' stability and,frequently, it is necessary to break down a persistent foam or frothgenerated in a froth flotation process by using defoamer agents.

The use of a defoamer after separation of the froth from the calciumcarbonate however requires another step usually to be conducted outsideof the flotation cell.

Hence, there is a continued need to optimize the reverse froth flotationprocess of purifying calcium carbonate ores, particularly by avoiding anadditional step of froth breakdown. The foam formed should be stableenough to just float the impurity mineral particles out of the flotationcell and should break after being discharged from the flotation cell.

In addition, it is particularly important to achieve a magnesium oxidegrade of 5.5 wt.-% or less, a high calcium oxide grade and high massrecovery in the flotation process product.

In the instantly described process for reverse flotation of calciumcarbonate, antifoam is added together with the collector to avoidexcessive foaming without affecting the mineral-collector interaction.The presence of stable foam or froth is prevented by avoiding theformation of stable air bubbles by using antifoam agents that do notaffect the mineral-collector interaction. The expression antifoamsherein is used for chemicals designed to prevent the formation of stablefoam (herein also referred to as antifoam agents). In the state of theart such chemicals are also referred to as foam inhibitors. They are tobe distinguished from defoamers which break the existing foam.

Antifoams are added together with the collector in order to preventstable foam from forming. Antifoams act throughout the flotation cell toprevent excess foam generation and stability. There are differentcompounds that can be used as antifoam. Any chemical compound that hasdestabilizing effects on the foam is suitable as antifoam.

The use of antifoam agents reduces the amount of foam formed from thequaternary ammonium compounds during the flotation process. It isdesired that the foam stability decreases after the flotation process.It is desired that any foam should be broken before pumping theflotation cell discharge to the tailing dam.

The instant invention therefore relates to a composition, comprising

-   -   A) at least one quaternary ammonium compound which is a        collector for the reverse flotation of magnesium minerals from        calcium carbonate,    -   B) at least one antifoam agent, and    -   C) at least one solvent.

This invention further relates to the use of the composition accordingto the invention as flotation reagent in the reverse flotation ofmagnesium silicate minerals from calcium carbonate ore.

This invention further relates to a process for reversely floatingmagnesium silicate minerals from calcium carbonate ore, the processcomprising adding the inventive composition to a flotation cellcontaining magnesium silicate minerals and calcium carbonate ore inaqueous slurry, subsequently flowing air through the flotation cell andremoving the magnesium silicate minerals together with the foam sogenerated.

The composition of the invention comprises at least one quaternaryammonium compound collector preferably in an amount of 20 to 60 wt.-%,in particular in the amount of 30 to 50 wt.-%, particularly preferred 35to 45 wt.-%.

The amount of antifoam agent in the composition is preferably at most 25wt.-%, particularly at most 20 wt.-%, more preferably at most 15 wt.-%.A preferred lower limit for the amount of antifoam agent is 5 wt.-%,more preferably 10 wt.-%.

The amount of solvent is preferably up to 75 wt.-%, more preferably 50to 70 wt.-%, most preferable 55 to 65 wt.-%. In another preferredembodiment, the amount of solvent is the balance to 100 wt.-% from thecombined amounts of collector and antifoam. Preferred solvents arewater, ethanol, isopropanol, 2-ethylhexanol and paraffin, or mixturesthereof. The term “paraffin” means a liquid composition of hydrocarbonswhich are preferably saturated and aliphatic. Their solidification pointis preferably below −6° C. The use of paraffin is particularly suitablein cases where the odor from alcohols is to be avoided.

In accordance with Ullmann's Encyclopedia of Industrial Chemistry, Foamand Foam Control, (2012) Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim,antifoam agents are frequently used in the form of composites. Thefunctional chemical compounds present in such composites which are usedas antifoam agents can be divided into four categories:

1. Carrier oils

2. Active ingredients

3. Amphiphilic substances

4. Coupling and stabilizing agents

Carrier oils themselves have foam-control capability. They includewater-insoluble paraffinic and naphthenic mineral oils, vegetable oilssuch as tall oil, castor oil, soybean oil or peanut oil, residues fromthe oxo alcohol synthesis, alkylbenzenes, and crude oils from thelow-temperature carbonization of brown coal or other bituminousmaterials.

In the present invention carrier oils preferably are mineral oils(naphthenic, aromatic and paraffinic), alkyl benzenes, and vegetableoils, e.g. soy oil.

Preferred alkyl benzenes are reaction products from olefins and benzeneby alkylation, olefin dimerization, benzene dialkylation, olefindiphenyl or benzene cycle addition.

Preferred alkyl benzenes are selected from the group consisting of alkylbenzenes (1), biphenyl alkanes (2), dialkyl benzenes (3),1,3-dialkylindanes (4) and 1,4-dialkyltetralines (5) according to theformulae 1-5

wherein

-   -   R¹ and R² are independently from each other hydrocarbon groups        having from 1 to 30, particularly from 2 to 10 carbon atoms.

In one preferred embodiment, R¹ and/or R² is a saturated or unsaturated,branched or linear C₆ to C₃₀ aliphatic hydrocarbon group or a C₆ to C₃₀aromatic hydrocarbon group. In another preferred embodiment, R¹ and R²are independently from each other alkyl groups with 1 to 30, preferably2 to 10 carbon atoms, or C₁₀- to C₁₃-alkenyl groups.

The paraffinic and naphthenic mineral oils may be used in bothfunctions, antifoam and coupling and stabilizing agent.

Active ingredients are compounds generally insoluble in the foamingmedium and having surface active properties. An essential feature of anactive ingredient is a low viscosity and a facility to spread rapidly onfoamy surfaces. It has affinity to the air-liquid surface where itdestabilizes the foam lamellas. This causes rupture of the air bubblesand breakdown of surface foam. Entrained air bubbles are agglomerated,and the larger bubbles rise to the surface of the bulk liquid morequickly.

There are some different classes of chemicals useful as activeingredients.

Silicone oils are particularly effective antifoaming agents because oftheir low surface tension, thermal stability, chemical inertness, andtotal water insolubility. By far the most important silicone oils arethe dimethylpolysiloxanes, in which chain ends are saturated withtrimethylsilyl groups. The number of siloxane units present rangespreferably from 2 to 2000.

In the case that dimethylpolysiloxanes by themselves show littlefoam-inhibiting activity with respect to aqueous surfactant solutions,they may be used in form of formulations supplemented with finelydivided hydrophobic solid particles. These particles presumably conferthe actual foam-inhibiting properties, while the silicone oil acts ashydrophobic carrier oil that offers unusually good spreading properties.

Hydrophobic Silica is another class of active ingredients. The normallyhydrophilic silica is made hydrophobic e.g. by

-   -   1. spraying the silica with silicone oil and tempering at        250-350° C.,    -   2 treatment with organosilicon halide vapors in an autoclave,        and    -   3. dispersing the silica in a silicone oil at elevated        temperature and recovery of the solid by centrifugation.

Hydrophobic silica can also be produced by reacting silica hydrogel withalcohols, fatty amines, or wax. Amorphous, precipitated silica with aparticle size of 1-2 μm is the most suitable starting material forfoam-inhibiting agents.

Hydrophobic fats and waxes useful as active ingredients include thefollowing materials:

-   -   1. fatty acid esters of monofunctional and polyfunctional        alcohols;    -   2. fatty acid amides and sulfonamides;    -   3. paraffinic hydrocarbon waxes, ozokerite, and montan wax;    -   4. phosphoric acid mono-, di-, and triesters of fatty alcohols,        in case of the triesters, also tributyl phosphate and        tributoxyethyl phosphate have foam-inhibiting properties;    -   5. natural or synthetic fatty alcohols;    -   6. water-insoluble soaps of fatty acids, including aluminum        stearate, calcium stearate, and calcium behenate;    -   7. perfluorinated fatty alcohols.

Unless noted otherwise, the terms “fatty” and “long chain” with respectto a carbon atom chain length, e.g. in a fatty acid or fatty alcohol,means a saturated or unsaturated straight chain of 6 to 30, preferably 8to 24 carbon atoms.

A number of water-insoluble polymers may be used as active ingredients,including, fatty acid modified alkyl resins; novolaks; copolymers ofvinyl acetate and long-chain maleic and fumaric acid diesters; andmethyl methacrylate-vinylpyrrolidone copolymers. Other relevantpolymeric materials include poly(propylene glycols) and propylene oxideadducts to glycerol, trimethylol-propane(1,1,1-tris(hydroxymethyl)propane), pentaerythritol, triethanolamine,dipentaerythritol, or polyglycerol.

Addition products of butylene oxide or long-chain a-epoxides withpolyvalent alcohols show the same effects as propylene oxide polymers.

Molecular weights of such polymers may range from the lowest possiblemolecular weight (two units) up to 5000 g/mol, preferably 250 to 3000g/mol, more preferably 400 to 1100 g/mol.

Amphiphilic substances are components with varying water solubilitywhose foam-inhibiting effects are due to a variety of mechanisms.Preferred as amphiphilic substances are nonionic surfactants, preferablyethoxylated fatty alcohols, fatty acids, rosin acids, fatty amines andalkylphenol derivatives with HLB values<10.

In the present invention, amphiphilic substances used as antifoams arepreferably alkoxylated fatty alcohols. Preferred alkoxylated fattyalcohols correspond to the formulae

R—O-(A-O)_(n)—H   (6)

R—O-(A-O)_(n)—(B—O)_(m)—H   (7)

wherein

-   -   R is a saturated or unsaturated, branched or linear C₆ to C₃₀        aliphatic hydrocarbon group or a C₆ to C₃₀ aromatic hydrocarbon        group,    -   n is a number from 1 to 30, preferably a number from 2 to 10,        and    -   m is a number from 1 to 30, preferably a number from 2 to 10,        and    -   A and B are independently from each other C₂- to C₄-alkylene        groups with the proviso that A is different from B.

In formulae (6) and (7), A is preferably a C₂-alkylene group and B ispreferably a C₃- or C₄-alkylene group. R is preferably a C₈- toC₂₀-alkenyl group or a C₇- to C₂₀-alkylaryl group. Formula (6) denotes apolyoxyalkylene homopolymer or a polyoxyalkylene random copolymer.Formula (7) denotes a polyoxyalkylene block copolymer.

For the purpose of the instant invention the term antifoam comprisespreferably the above-mentioned categories carrier oil, activeingredients and amphiphilic substances or mixtures thereof.

The collector of the instant invention is a quaternary ammoniumcompound. The quaternary ammonium compound of the present invention, inone preferred embodiment corresponds to the formula

[R¹R²R³R⁴N]⁺X⁻  (8)

wherein

-   -   R¹, R², R³, and R⁴ independently are linear, branched, cyclic,        saturated or unsaturated hydrocarbon groups, and    -   X is an anion.    -   R¹, R², R³ and R⁴ preferably contain between 1 and 30,        particularly 2 to 20 carbon atoms, provided that at least one of        R¹, R², R³ and R⁴ contains from 6 to 20 carbon atoms. The sum of        the number of carbon atoms in R¹, R², R³, and R⁴ preferably        ranges from 9 to 35, particularly from 10 to 30. R¹, R², R³, and        R⁴ may be alkyl, alkenyl, alkynyl, cycloalkyl or aryl groups.    -   X may be chloride, carbonate, bicarbonate, nitrate, bromide,        acetate or carboxylate.

A preferred quaternary ammonium compound corresponds to the formula

[R¹(CH₃)₃N]⁺X⁻  (9)

wherein

-   -   R¹ is a linear or branched C₆-C₂₀ saturated or unsaturated        hydrocarbon group, such as an alkyl, alkenyl, or alkynyl group,        and X is as defined above.

More preferably,

-   -   R¹ is a linear C₆-C₁₈ saturated or unsaturated hydrocarbon group        and    -   X is chloride, carbonate, or acetate.

Another preferred quaternary ammonium compound corresponds to theformula

[R¹R²(CH₃)₂N]⁺X⁻  (10)

wherein

-   -   R¹ is a linear or branched C₆-C₂₀ saturated or unsaturated        hydrocarbon group or a C₆-C₂₀ substituted aryl group, benzyl or        an unsubstituted aryl group,    -   R² is a linear or branched C₁-C₂₀ saturated or unsaturated        hydrocarbon group or C₆-C₂₀ substituted aryl group, benzyl or an        unsubstituted aryl group, and    -   X is as defined above.

Preferably,

-   -   R¹ and R² independently are linear or branched C₈-C₁₆ saturated        or unsaturated hydrocarbon groups. In a more preferred        embodiment, R¹ and R² independently are linear or branched        C₈-C₁₂ saturated or unsaturated hydrocarbon groups, and    -   X is chloride, carbonate, sulfate, or acetate.

The expression “substituted” as used herein means substitution with aC₁-C₄-alkyl group, unless defined otherwise.

Another preferred quaternary ammonium compound corresponds to theformula

[R¹R²(CH₃)₂N]⁺X⁻  (11)

wherein

-   -   R¹ is a benzyl group,    -   R² is a linear C₁₀ to C₂₀ saturated or unsaturated hydrocarbon        group, and    -   X is defined as above.

According to a preferred embodiment, R¹ is benzyl, R² is a linearC₁₂-C₁₈ saturated or unsaturated hydrocarbon group, and X⁻ is chloride.

Another quaternary ammonium compound preferred for use in the presentinvention corresponds to the formula

[R¹R²N(CH₃)((CH₂CH₂O)_(n)H)]⁺X⁻  (12)

wherein

-   -   R¹ is a C₆-C₂₀ hydrocarbon group, particularly linear or        branched, substituted or unsubstituted alkyl group or a C₆-C₂₀        substituted or unsubstituted aryl group,    -   R² is a hydrocarbon group, particularly a C₁-C₂₀ linear or        branched, substituted or unsubstituted alkyl group or a C₆-C₂₀        substituted or unsubstituted aryl group,    -   n is an integer from 1 to 5, and    -   X is defined as above.

Preferably,

-   -   R¹ and R² are linear or branched C₈-C₁₀ substituted or        unsubstituted alkyl or aryl groups and more preferably are        decyl.    -   X⁻ is preferably chloride.

Another preferred quaternary ammonium compound corresponds to theformula

[R¹R²R³(CH₃)N]⁺X⁻  (13)

wherein

-   -   R¹, R² and R³ independently are linear or branched C₆-C₂₀        saturated or unsaturated hydrocarbon groups.

More preferably

-   -   R¹, R² and R³ independently are linear or branched C₈-C₁₀        saturated or unsaturated hydrocarbon groups.    -   X is preferably chloride.

The composition according to this invention is added to ores in anamount of 100 to 5000, preferably 200 to 4000 g/tons of ore.

All percentages in this specification mean weight percent, unless notedotherwise.

EXAMPLES

Froth flotation experiments were conducted using a Denver laboratoryflotation cell. Around 0.4 kg of ground ore was conditioned (1200 rpm)with 0.6 liters of water (solid pulp 40%). The collector was added and1.6 l of water was added to adjust the cell flotation water content(solid pulp 15%). The pH was adjusted to 9.5 and the mixture was stirredfor 2 minutes. The air intake was opened and the ore was floated during5 minutes, obtaining the rougher concentrated and tailings. The productsobtained were transferred to a tray and dried at 105±5° C., following tobe weighed and analyzed to determine the magnesium oxide and calciumoxide grade.

The solid pulp comprises the solid mass percentage in function of totalmass percentage (solid+water) at the flotation cell.

Description of the Cylinder Foam Test: For foam stability evaluation 100ml of the inventive emulsion were prepared and transferred to a measuredcylinder of 500 ml capacity. The cylinder was shaken 10 times in a 180°movement. After the 10^(th) movement, the chronometer was started andthe foam height was measured at the start and every minute for 5minutes. This cylinder foam test was also performed in the presence ofore simulating the pulp solid content.

Description of the Ross Miles Test (ASTM D1173/1980): In the Ross milesgraduated column (1 m height) the inventive emulsion was added to reachthe 0.0 ml demarcation. Another aliquot was transferred to the ampoule(200 ml) and coupled at the top of the graduated column. Then the liquidwas release from the ampoule for free fall. The chronometer is startedafter the total liquid fell and the foam height is checked at the startand every minute for 5 minutes.

Inventive Composition Preparation:

The quaternary ammonium compound is heated to a temperature of 50° C.until all solids are molten, and is homogenized. Some homogenizedquaternary ammonium compound is weighed into a beaker at 25° C. and theantifoam is added while stirring at around 100 rpm. Then, the solvent isadded slowly while stirring for 30 minutes until complete homogenizationis achieved. The obtained composition is clear and of yellowish colour.

Materials used:

Praepagen® WB=Distearyl dimethyl ammonium chloride (Clariant S/A)

Flotigam® K2C=Dimethyl Dicocoalkyl Ammonium Chloride (Clariant S/A)

Genamin® T 150=Alkylamine ethoxylated (Clariant S/A)

Detalp® 360=Alkyl benzenes (Deten Quimica S/A)

Isocer® NL=Paraffinic oil (Isogama)

Example 1

Inventive composition 1 (table 1) was compared with a standard productin a froth flotation test. The standard product is believed to comprisea dicoco dimethyl quaternary ammonium salt solved in isopropanol. Itdoes not contain a defoamer.

TABLE 1 Inventive Composition 1 for flotation test evaluationComposition content (wt.-%) Chemical compound 1 42 Praepagen WB 10Detalp 360 5 Nonylphenol-4EO 34 Ethanol 9 Water

The flotation test results are presented at table 2, in which theinventive composition 1 presents a higher calcium recovery with a MgOcontent below 5.5 wt.-%, compared with the standard product results.

TABLE 2 Flotation performance comparison test Composition Dosage (g/ton)% MgO CaO-Recovery (%) 1 300 4.90 83.4 standard product 300 4.23 77.0 1400 4.76 78.9 standard product 400 4.40 72.8

The foam tests were conducted comparing the composition 1 and standardproduct. The results (table 3) shows a lower foam in the presence of theantifoam agent.

TABLE 3 Foam height test comparing composition 1 and standard product.Foam Height (ml) Time (min) Cylinder Cylinder Foam Test Ross Miles(without ore) (with ore) Composition 1 Standard 1 Standard 1 StandardInstant 50.0 232.5 27.5 185.0 13.3 133.3 0.5 22.5 230.0 22.5 185.0 13.3133.3 1 17.5 230.0 17.5 185.0 13.3 133.3 2 15.0 230.0 15.0 185.0 11.6131.6 3 15.0 230.0 12.5 182.5 11.6 130.0 4 15.0 227.5 10.0 182.5 10.0130.0 5 15.0 227.5 10.0 182.5 10.0 130.0

It can be concluded that composition 1 presents a lower foam formationand higher calcium recovery than the standard product.

Example 2

Inventive composition 2 was compared with the composition 2-A (both asdefined in table 4) in a froth flotation test. The flotation testresults are presented at table 5, in which emulsion composition 2presents a slightly higher calcium recovery with a MgO content in bothcases below 5.5 wt.-%.

TABLE 4 Composition 2 and 2-A for flotation test evaluation CompositionFormulation (%) Chemical compound 2 42 Praepagen WB 10 Detalp 360 5Nonylphenol-4EO 10 2-Ethylhexanol 15 Ethanol 18 Water 2-A 42 PraepagenWB 10 Detalp 360 5 Nonylphenol-4EO 10 Isocer NL 33 Ethanol

Composition 2-A avoids the use of 2-Ethylhexanol for odor reasons.2-Ethylhexanol is replaced by the paraffin Isocer.

Table 5: Flotation Performance Comparison Test

TABLE 5 Flotation performance comparison test Composition Dosage (g/ton)% MgO CaO-Recovery (%) 2 200 5.75 85.0 2-A 200 5.70 86.0 2 500 5.19 85.02-A 500 5.33 86.0

It becomes apparent that the replacement of 2-Ethylhexanol by a paraffindoes not impede the utility of the claimed invention.

Example 3

The cylinder foam tests were conducted comparing the quaternary ammoniumcompound in its pure form (comparative) and in the inventive formtogether with antifoam (compositions see Table 6). The results show alower foam in the presence of the antifoam agent (composition 3-A, 4-Aand 5-A). Both tests with and without ore presented a lower foam, in thepresence of the antifoam agent (table 7 and 8).

TABLE 6 Foam test products composition and solution percentageComposition Solution (%) Chemical compound 3 (comp.) 0.350 Flotigam K2C3-A 0.350 Flotigam K2C 0.115 Detalp 360 0.050 Nonylphenol-4EO 4 (comp.)0.350 Praepagen WB 4-A 0.350 Praepagen WB 0.061 Detalp 360 0.030Nonylphenol-4EO 0.061 2-Ethyl Hexanol 5 (comp.) 0.257 Flotigam K2C 0.092Genamin T 150 5-A 0.257 Flotigam K2C 0.092 Genamin T 150 0.107 Detalp360 0.045 Nonylphenol-4EO

TABLE 7 Cylinder foam height test in the presence of the ore Time (min)Cylinder (with ore)-Foam Height (ml) Composition 3 3-A 4 4-A 5 5-AInstant 82.5 47.5 22.5 15.0 170.0 157.5 0.5 80.0 47.5 22.5 15.0 170.0157.5 1 77.5 47.5 22.5 15.0 170.0 157.5 2 77.5 47.5 22.5 15.0 167.5157.5 3 77.5 47.5 22.5 15.0 167.5 155.0 4 77.5 47.5 22.5 15.0 167.5155.0 5 75.0 47.5 22.5 15.0 167.5 155.0

TABLE 8 Cylinder foam height test without the ore Time (min) Cylinder(without ore)-Foam Height (ml) Composition 3 3-A 4 4-A 5 5-A Instant67.5 45.0 32.5 20.0 135.0 120.0 0.5 67.5 45.0 30.0 20.0 135.0 120.0 167.5 45.0 30.0 20.0 135.0 115.0 2 67.5 45.0 30.0 20.0 135.0 110.0 3 67.542.5 27.5 17.5 130.0 105.0 4 67.5 40.0 27.5 15.0 127.5 102.5 5 67.5 40.027.5 15.0 125.0 102.5

Example 4

The Ross Miles foam tests were conducted comparing the foamingproperties of quaternary ammonium compounds in absence of ore, with andwithout the presence of an antifoam agent (table 6). The results (table9) shows a lower foam in the presence of the antifoam agent (composition4-A and 5-A).

TABLE 9 Ross Miles foam height test without the ore Ross Milles (withoutore) - Time (min) Foam Height (ml) Composition 4 4-A 5 5-A Instant 47.535.0 252.5 240.0   0.5 47.5 32.5 252.5 240.0 1 47.5 32.5 252.5 240.0 247.5 30.0 252.5 240.0 3 47.5 30.0 252.5 240.0 4 47.5 25.0 252.5 240.0 547.5 25.0 252.5 240.0

1-26. (canceled)
 27. A process for reversely flotating magnesiumsilicate minerals from calcium carbonate ore, the process comprisingadding a composition comprising A) at least one quaternary ammoniumcompound which is a collector for the reverse flotation of magnesiumminerals from calcium carbonate, B) at least one antifoam agent, and C)at least one solvent to a flotation cell containing magnesium silicateminerals and calcium carbonate ore, subsequently flowing air through theflotation cell and removing the magnesium silicate minerals with thefoam so generated.
 28. The process according to claim 27, wherein thequaternary ammonium compound corresponds to formula (8)[R¹R²R³R⁴N]⁺X⁻  (8) wherein R¹, R², R³ and R⁴ independently from eachother are hydrocarbon groups containing 1 to 30 carbon atoms, with theproviso that at least one of R¹, R², R³ and R⁴ contains between 6 and 20carbon atoms, and X is selected from the group consisting of chloride,carbonate, bicarbonate, nitrate, bromide, acetate or carboxylate. 29.The process according to claim 28, wherein the total number of carbonatoms contained in R¹, R², R³ and R⁴ is from 9 to
 35. 30. The processaccording to claim 28, wherein the quaternary ammonium compoundcorresponds to formula (9)[R¹(CH₃)₃N]⁺X⁻  (9) wherein R¹ is a C₆-C₂₀ hydrocarbon group.
 31. Theprocess according to claim 28, wherein the quaternary ammonium compoundcorresponds to formula (10)[R¹R²(CH₃)₂N]⁺X⁻  (10) wherein both R¹ and R² are C₆-C₂₀ hydrocarbongroups.
 32. The process according to claim 28, wherein the quaternaryammonium compound corresponds to formula (11)[R¹R²(CH₃)₂N]⁺X⁻  (11) wherein R¹ is a benzyl group and R² is a linearC₁₀ to C₂₀ hydrocarbon group.
 33. The process according to claim 28,wherein the quaternary ammonium compound corresponds to formula (12)[R¹R²N(CH₃)((CH₂CH₂O)_(n)H)]⁺X⁻  (12) wherein both R¹ and R² areindependently a C₆-C₂₀ hydrocarbon group, and n is an integer from 1 to5.
 34. The process according to claim 28, wherein the quaternaryammonium compound corresponds to formula (13)[R¹R²R³(CH₃)N]⁺X⁻  (13) wherein R¹, R² and R³ independently are linearor branched C₆-C₂₀ saturated or unsaturated hydrocarbon groups.
 35. Theprocess according to claim 27, wherein X is chloride.
 36. The processaccording to claim 27, wherein the amount of component A is from 20 to60 wt.-%.
 37. The process according to claim 27, wherein the amount ofcomponent B is from 5 to 25 wt.-%.
 38. The process according to claim27, wherein the amount of component C is from 15 to 75 wt.-%.
 39. Theprocess according to claim 27, wherein the solvent is selected from thegroup consisting of water, ethanol, isopropanol, 2-ethylhexanol andparaffin, or mixtures thereof.
 40. The process according to claim 27,wherein the antifoam agent comprises at least one component selectedfrom the group consisting of insoluble paraffinic and napthenic mineraloils, vegetable oils, residues from the oxo alcohol synthesis,alkylbenzenes, and crude oils from the low-temperature carbonization ofbrown coal or other bituminous materials.
 41. The process according toclaim 27, wherein the antifoam agent comprises at least one componentselected from the group consisting of the compounds according to theformulae 1 to 5

wherein R¹ and R² are independently from each other hydrocarbon groupshaving from 1 to 30, particularly from 2 to 10 carbon atoms.
 42. Theprocess according to claim 27, wherein the antifoam agent comprises atleast one dimethylpolysiloxane having 2 to 2000 siloxane groups.
 43. Theprocess according to claim 27, wherein the antifoam agent comprises atleast one hydrophobic silica.
 44. The process according to claim 27,wherein the antifoam agent comprises at least one hydrophobic fat or waxselected from the group consisting of (1) fatty acid esters ofmonofunctional and polyfunctional alcohols; (2) fatty acid amides andsulfonamides; (3) paraffinic hydrocarbon waxes, ozokerite, and montanwax; (4) phosphoric acid mono-, di-, and triesters of short- andlong-chain fatty alcohols; (5) short- and long-chain natural orsynthetic fatty alcohols; (6) water-insoluble soaps of long-chain fattyacids; and (7) perfluorinated fatty alcohols.
 45. The process accordingto claim 27, wherein the antifoam agent comprises at least onewater-insoluble polymer selected from the group consisting of fatty acidmodified alkyd resins; novolak resins; copolymers of vinyl acetate andlong-chain maleic and fumaric acid diesters; methylmethacrylate-vinylpyrrolidone copolymers; poly(propylene glycols);propylene oxide adducts to glycerol, trimethylolpropane,(1,1,1-tris(hydroxymethyl)propane), pentaerythritol, triethanolamine,dipentarythritol and polyglycerol.
 46. The process according to claim27, wherein the antifoam agent comprises at least one ethoxylatedalcohol corresponding to the formulae (6) and (7)R—O-(A-O)_(n)—H   (6)R—O-(A-O)_(n)—(B—O)_(m)—H   (7) wherein n is a number from 1 to 30 m isa number from 1 to 30 A is a C₂- to C₄-alkylene group B is a C₂- toC₄-alkylene group R is a C₆- to C₃₀-hydrocarbon group.
 47. The processaccording to claim 46, wherein n and m independently are numbers from 2to
 10. 48. The process according to claim 36, wherein R is selected fromthe group consisting of alkyl and alkenyl groups.
 49. The processaccording to claim 46, wherein formula (6) denotes a polyoxyalkylenehomopolymer or a polyoxyalkylene random copolymer.
 50. The processaccording to claim 46, wherein formula (7) denotes a polyoxyalkyleneblock copolymer.
 51. The process according to claim 46, wherein A is aC₂-alkylene group and B is a C₃- or C₄-alkylene group.